Inductive-capacitive filters and associated systems and methods

ABSTRACT

An inductive-capacitive filter includes a first insulating-conductive strip wound around a winding axis, where the first insulating-conductive strip includes a first conductive strip joined with a first insulating strip. An inductive-capacitive filter assembly includes a first and a second insulating-conductive strip concentrically wound around a winding axis, the first insulating-conductive strip including a first conductive strip joined with a first insulating strip, and the second insulating-conductive strip including a second conductive strip joined with a second insulating strip.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/633,409, filed Jan. 23, 2020, now U.S. Pat. No. 11,183,985 B2 issuedon Nov. 23, 2021, which is a § 371 national stage of InternationalPatent Application No. PCT/US2018/043651, filed Jul. 25, 2018, whichclaims benefit of priority to U.S. Provisional Patent Application Ser.No. 62/536,806, filed Jul. 25, 2017, each of which is incorporatedherein by reference.

BACKGROUND

Selective electrical signal elimination is often critical to stable andreliable operation of equipment that delivers high power radio frequency(RF) electrical signals, such as electrical signals between 10 kilohertz(kHz) and 1 gigahertz (GHz). In some applications electrical signalsmust be removed within a specified bandwidth, necessitating use of abandstop filter which blocks electrical signals having frequencieswithin a certain frequency band while transmitting electrical signals orelectrical energy outside of the frequency band. Additionally, someapplications require electrical energy to be delivered to multiple loadshaving the same or different selective signal elimination requirements.These multi-load applications require a bandstop filter for each load,where each bandstop filter is tuned for its specific load, and whereeach bandstop filter does not significantly interfere with each otherbandstop filter.

A bandstop filter ideally has high impedance at a specified frequencyband to block signals within the specified frequency band, while havinglow impedance outside of the frequency band to prevent undesired signalattenuation and/or inefficient delivery of electrical energy. A filter'ssignal attenuation as a function of signal frequency may be referred toas the filter's bandstop characteristics. Bandstop filters areconventionally constructed from two or more discrete components, such asa discrete inductor and a discrete capacitor placed in a parallelconfiguration in an electrical circuit. The discrete inductor istypically formed of copper or aluminum wire wound in a coil, and thecoil is optionally wound around a magnetic core. The discrete capacitoris typically formed of two metal plates with a dielectric material inbetween the two metal plates. The dielectric material can be ceramic,glass, mica, plastic film, or metal oxide.

SUMMARY

In an embodiment, an inductive-capacitive filter includes a firstinsulating-conductive strip wound around a winding axis, where the firstinsulating-conductive strip includes a first conductive strip joinedwith a first insulating strip.

In an embodiment, the first conductive strip is wound in parallel withthe first insulating strip around the winding axis.

In an embodiment, the first conductive strip is formed of metallic foil,and the first insulating strip is formed of dielectric material.

In an embodiment, the first conductive strip has a cross-sectional areawith an aspect ratio of at least 2.

In an embodiment, the first insulating-conductive strip forms an inneraperture, as seen when the inductive-capacitive filter is viewedcross-sectionally along a direction of the winding axis.

In an embodiment, the inner aperture has a non-circular shape.

In an embodiment, the inductive-capacitive filter further includes amagnetic core disposed in the inner aperture.

In an embodiment, the inductive-capacitive filter further includes firstand second terminals electrically coupled to opposing first and secondends of the first conductive strip, respectively.

In an embodiment, the inductive-capacitive filter further includes oneor more additional insulating-conductive strips wound around the windingaxis, each additional insulating-conductive strip including a respectiveconductive strip wound with a respective insulating strip.

In an embodiment, a inductive-capacitive filter assembly includes afirst and a second insulating-conductive strip concentrically woundaround a winding axis, the first insulating-conductive strip including afirst conductive strip joined with a first insulating strip, and thesecond insulating-conductive strip including a second conductive stripjoined with a second insulating strip.

In an embodiment, the first conductive strip is wound in parallel withthe first insulating strip around the winding axis, and the secondconductive strip is wound in parallel with the second insulating striparound the winding axis.

In an embodiment, the first insulating-conductive strip is electricallycoupled to the second insulating-conductive strip.

In an embodiment, the first insulating-conductive strip is disposedwithin the second insulating-conductive strip, as seen when theinductive-capacitive filter assembly is viewed cross-sectionally along adirection of the winding axis.

In an embodiment, the inductive-capacitive filter assembly furtherincludes a third insulating-conductive strip concentrically wound withthe first and second insulating-conductive strips around the windingaxis. The third insulating-conductive strip includes a third conductivestrip joined with a third insulating strip, and each of the first,second, and third insulating-conductive strips form a respectiveinductive-capacitive filter. The first insulating-conductive strip isdisposed within the second insulating-conductive strip, as seen when theinductive-capacitive filter assembly is viewed cross-sectionally along adirection of the winding axis, and each of the first and secondinsulating conductive strips is disposed within the thirdinsulating-conductive strip, as seen when the inductive-capacitivefilter assembly is viewed cross-sectionally along the direction of thewinding axis.

In an embodiment, each of the first and second conductive strips isformed of metallic foil, and each of the first and second insulatingstrips is formed of dielectric material.

In an embodiment, the first conductive strip has a cross-sectional areawith an aspect ratio of at least 2, and the second conductive strip hasa cross-sectional area with an aspect ratio of at least 2.

In an embodiment, each of the first and second insulating-conductivestrips forms multiple turns around the winding axis.

In an embodiment, each of the first and second insulating-conductivestrips forms a different respective number of turns around the windingaxis.

In an embodiment, the inductive-capacitive filter assembly furtherincludes a third insulating-conductive strip concentrically wound withthe first and second insulating-conductive strips around the windingaxis. The third insulating-conductive strip includes a third conductivestrip joined with a third insulating strip, and each of the first,second, and third insulating-conductive strips forming a respectiveinductive-capacitive filter.

In an embodiment, an electrical circuit includes any of theabove-disclosed inductive-capacitive filters.

In an embodiment, opposing first and second ends of the first conductivestrip are electrically coupled to different respective nodes of theelectrical circuit.

In an embodiment, the electrical circuit further includes a load and atleast one of an alternating current electrical power source and a directcurrent electrical power source electrically coupled in series with theinductive-capacitive filter of the electrical circuit.

In an embodiment, an electrical circuit includes any one of theabove-disclosed inductive capacitive filter assemblies, and each of thefirst and second insulating-conductive strips are electrically coupledto respective branches of the electrical circuit.

In an embodiment, each of the first and second insulating-conductivestrips is electrically coupled between an electrical power source and arespective electrical load.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an inductive-capacitive-filter,according to an embodiment.

FIG. 2 is a cross-sectional view of the FIG. 1inductive-capacitive-filter.

FIG. 3 illustrates an approximate electrical model of the FIG. 1inductive-capacitive-filter.

FIG. 4 is a graph of impedance versus frequency of one particularembodiment of the FIG. 1 inductive-capacitive filter.

FIG. 5 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but has six turns instead offour turns, according to an embodiment.

FIG. 6 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but has a larger inneraperture, according to an embodiment.

FIG. 7 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but has an inner aperturewith an oval shape, according to an embodiment.

FIG. 8 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but with a differentinsulating strip, according to an embodiment.

FIG. 9 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but has a thicker insulatingstrip, according to an embodiment.

FIG. 10 is a cross-sectional view of the FIG. 9inductive-capacitive-filter.

FIG. 11 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but has a thicker conductivestrip, according to an embodiment.

FIG. 12 is a cross-sectional view of the FIG. 11inductive-capacitive-filter.

FIG. 13 is a perspective view of an inductive-capacitive filter which islike the FIG. 1 inductive-capacitive filter but with a widerinsulating-conductive strip, according to an embodiment.

FIG. 14 is a perspective view of an inductive-capacitive filter assemblyincluding two inductive-capacitive filters in a single device, accordingto an embodiment.

FIG. 15 illustrates the inductive-capacitive filter assembly of FIG. 14with first and second insulating-conductive strips electrically coupledin series, according to an embodiment.

FIG. 16 illustrates an approximate electrical model of the FIG. 14inductive-capacitive filter assembly when electrically coupled asillustrated in FIG. 15 .

FIG. 17 is a graph of impedance versus frequency of one particularembodiment of the FIG. 14 inductive-capacitive filter assembly whenelectrically coupled as illustrated in FIG. 15 .

FIG. 18 illustrates the inductive-capacitive filter assembly of FIG. 14with first and second insulating-conductive strips electrically coupledin parallel, according to an embodiment.

FIG. 19 is a graph of impedance versus frequency of one particularembodiment of the FIG. 14 inductive-capacitive filter assembly whenelectrically coupled as illustrated in FIG. 18 .

FIG. 20 is a perspective view of two inductive-capacitive filterselectrically coupled in series, according to an embodiment.

FIG. 21 is a graph of impedance versus frequency of one particularembodiment of the FIG. 20 inductive-capacitive filters electricallycoupled in series.

FIG. 22 is a perspective view of an inductive-capacitive filter assemblyincluding additional insulating-conductive strips, according to anembodiment.

FIG. 23 is a cross-sectional view of the FIG. 22inductive-capacitive-filter assembly.

FIG. 24 illustrates an approximate electrical model of the FIG. 22inductive-capacitive-filter assembly.

FIG. 25 is a cross-sectional view of an inductive-capacitive filterwhich is like the FIG. 1 inductive-capacitive filter but where a widthof an insulating strip is greater than a width of a conductive strip,according to an embodiment.

FIG. 26 illustrates a perspective view of an inductive-capacitive filterincluding a rod type magnetic core disposed in an inner aperture,according to an embodiment.

FIG. 27 illustrates a perspective view of another inductive-capacitivefilter including an E type magnetic core disposed in an inner aperture,according to an embodiment.

FIG. 28 illustrates a perspective view of another inductive-capacitivefilter including an U type magnetic core disposed in an inner aperture,according to an embodiment.

FIG. 29 illustrates a perspective view of yet anotherinductive-capacitive filter including a pot type magnetic core disposedin an inner aperture, according to an embodiment.

FIG. 30 illustrates an electrical circuit including an instance of theFIG. 1 inductive-capacitive filter, according to an embodiment.

FIG. 31 illustrates another electrical circuit including an instance ofthe FIG. 1 inductive-capacitive filter, according to an embodiment.

FIG. 32 illustrates an electrical circuit including an instance of theFIG. 22 inductive-capacitive filter assembly, according to anembodiment.

FIG. 33 illustrates an electrical circuit including an instance of theFIG. 14 inductive-capacitive filter assembly, according to anembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Conventional bandstop filters can generally achieve acceptable bandstopcharacteristics with careful design and construction. However, thediscrete components forming conventional bandstop filters often causethe filters to be large, costly, and difficult to construct, especiallyfor high power applications. Additionally, impedance of wire formingdiscrete inductors of conventional bandstop filters may significantlylimit maximum current capability of the filters, especially at highoperating frequencies where the skin-effect, i.e., tendency forhigh-frequency current to crowd near outer surfaces of the wire, issignificant. Furthermore, it can be difficult to achieve precisebandstop characteristics in conventional bandstop filters due toparasitic effects, including parasitic inductance and parasiticcapacitance of discrete components forming conventional bandstopfilters.

Applicant has developed inductive-capacitive filters and associatedassemblies which potentially overcome one or more of the above-discusseddrawbacks associated with conventional bandstop filters. Certainembodiments do not require discrete inductors or discrete capacitors,thereby promoting small filter size, low filter cost, and ease of filtermanufacturing. Additionally, certain embodiments can be readily tuned toachieve desired bandstop characteristics during filter design and/ormanufacturing, thereby achieving precise bandstop characteristics andpotentially minimizing the number of base filter designs required tosupport varying applications. Furthermore, particular embodimentsachieve relatively low-impedance at low and high frequencies outside apredetermined frequency band, thereby helping minimize resistive losses.Moreover, some embodiments form multiple LC filters in a single package.

FIG. 1 is a perspective view of an inductive-capacitive filter 100,which is one embodiment of the new inductive-capacitive filtersdeveloped by Applicant. Inductive-capacitive filter 100 includes aninsulating strip 108 and a conductive strip 110, collectively referredto as insulating-conductive strip 102, wound around a winding axis 104to form a plurality of turns 106. In this document, specific instancesof an item may be referred to by use of a numeral in parentheses (e.g.,turn 106(1)) while numerals without parentheses refer to any such item(e.g., turns 106). Although inductive-capacitive filter 100 isillustrated as having four turns 106, the number of turns may be varied,including whole or partial turns, without departing from the scopehereof. Conductive strip 110 is joined with an insulating strip 108,such that conductive strip 110 is wound in parallel with insulatingstrip 108 around winding axis 104. FIG. 2 is a cross-sectional view ofinductive-capacitive filter 100 taken along line 2A-2A of FIG. 1 .Insulating strip 108 is formed, for example, of a non-conductive,dielectric insulating material such as nomex, Kapton, mylar paper, orany other material which will provide electrical isolation betweenconductive strips 110. Conductive strip 110 is formed, for example, of ametallic foil, such as aluminum foil, copper foil, or any other materialwith a low electrical resistivity. In certain embodiments, insulatingstrip 108 and conductive strip 110 are separately formed and are woundtogether to form insulating-conductive strip 102, while in some otherembodiments, insulating strip 108 and conductive strip 110 are bondedtogether before the resultant insulating-conductive strip 102 is woundaround winding axis 104. For example, in a particular embodiment,insulating strip 108 is formed on conductive strip 110 using a filmdeposition technique before the resulting insulating-conductive strip102 is wound around winding axis 104.

Conductive strip 110 has opposing first and second ends 130 and 132,respectively. A first terminal 134 is electrically coupled to first end130, and a second terminal 136 is electrically coupled to second end132. First and second terminals 134 and 136 provide electrical interfaceto inductive-capacitive filter 100. In some embodiments, first andsecond terminals 134 and 136 include a respective aluminum or copperbuss bar or wire soldered to conductive strip 110. First and secondterminals 134 and 136 could be omitted without departing from the scopehereof.

Conductive strip 110 has a cross-sectional area 112 when viewed in aplane parallel to each of winding axis 104 and a radial axis 114. Radialaxis 114 is orthogonal to winding axis 104 and extends away from windingaxis 104. Cross-sectional area 112 has an aspect ratio of width 116divided by thickness 118, where width 116 is a width of conductive strip110 parallel to winding axis 104 and thickness 118 is a thickness ofconductive strip 110 parallel to radial axis 114. In certainembodiments, the aspect ratio is at least 2, i.e., width 116 is at leasttwice thickness 118, to minimize the skin-effect and proximity effectswhen conductive strip 110 is carrying high-frequency signals. Asdiscussed above, the skin-effect describes the tendency of highfrequency current to crowd near outer surfaces of a conductor, while theproximity effect describes a magnetic field generated by current flowingthrough one conductor inducing a circulating current through one or morenearby other conductors. In a particular embodiment, thickness 118 is0.10 inch or less and width 116 is at least 0.5 inch or more to achievea large cross-sectional area 112, thereby promoting low AC resistanceand low DC resistance at frequencies outside of a bandstop filterfrequency band of inductive-capacitive filter 100.

Adjacent portions of conductive strip 110 create capacitance, andconductive strip 110 creates inductance when connected to an electricalcircuit. Consequently, inductive-capacitive filter 100 has electricalcharacteristics of a parallel inductive-capacitive filter. FIG. 3illustrates an approximate electrical model 300 of inductive-capacitivefilter 100 as seen from first and second terminals 134 and 136, where acapacitor 302 is electrically coupled in parallel with an inductivebranch 304. Inductive branch 304 includes an inductor 306 electricallycoupled in series with a resistor 308. Capacitor 302 representscapacitance of adjacent portions of conductive strip 110, inductorrepresents 306 inductance of conductive strip 110, and resistor 308represents resistance of conductive strip 110. Accordingly,inductive-capacitive filter 100 is capable of operating as a bandstopfilter without use of a discrete inductor or a discrete capacitor,thereby promoting small filter size, low filter cost, and ease of filtermanufacturing. Inductive-capacitive filter 100 has a resonant frequencyf₀, i.e. a frequency at which the filter has a peak impedance,approximately as follows, where L is inductance of inductor 306, and Cis capacitance of capacitor 302.f ₀=1/2π√{square root over (LC)}  EQN. 1

FIG. 4 is a graph 400 of impedance versus frequency of one particularembodiment of inductive-capacitive filter 100. As evident from FIG. 4 ,this particular embodiment has a resonant frequency of about 14.65megahertz (MHz), and impedance of the filter is approximately 30,000ohms at the resonant frequency. Impedance rapidly decreases whenfrequency moves away from the resonant frequency, such that theinductive-capacitive filter has a low impedance at frequencies away fromthe resonant frequency, to help minimize undesired signal attenuation.

It should be noted that although electrical model 300 of FIG. 3illustrates each of capacitor 302, inductor 306, and resistor 308 asbeing a discrete element for illustrative simplicity, each of thesecomponents represents a distributed element. Additionally, it should benoted that model 300 does not account for high-order effects, such as aleakage current through capacitor 302. It is anticipated thatinductive-capacitive filter 100 will typically be designed to promotesmall resistance of conductive strip 110 to minimize resistive losses ininductive-capacitive filter 100, although conductive strip 110 could bedesigned to achieve a finite resistance, such as in applications where aparticular resistive damping is desired.

The resonant frequency of inductive-capacitive filter 100 may be variedduring its design and/or manufacture, thereby enabling precise bandstopcharacteristics to be achieved and/or a single base design to supportnumerous applications. For example, the resonant frequency ofinductive-capacitive filter 100 may be varied by varying the number ofturns 106 formed around winding axis 104. In particular, increasing thenumber of turns 106 increases inductance of inductive-capacitive filter100, and increasing inductance lowers the resonant frequency ofinductive-capacitive filter 100, as can be determined from EQN. 1 above.FIG. 5 is a perspective view of an inductive-capacitive filter 500 whichis like inductive-capacitive filter 100 of FIG. 1 but having six turns106 instead of four turns 106. Accordingly, inductive-capacitive filter500 will have a lower resonant frequency than inductive-capacitivefilter 100. Only two instances of turns 106 are labeled in FIG. 5 topromote illustrative clarity. It should be noted that each turn 106 neednot necessarily be a complete turn, or in other words, the first and/orlast turn 106 could be a partial turn, which enables bandstopcharacteristics to be continuously varied during the design and/ormanufacture of inductive-capacitive filter 100.

Insulating-conductive strip 102 forms an inner aperture 120 and 520 ineach of inductive-capacitive filters 100 and 500, respectively, as seenwhen viewed cross-sectionally along a direction of winding axis 104.Bandstop characteristics of capacitive filters 100 and 500 can be variedby varying the size and/or shape of inner aperture 120 and 520, inaddition to or in place of varying the number of turns 106. For example,FIG. 6 is a perspective view of an inductive-capacitive filter 600 whichis like inductive-capacitive filter 100 of FIG. 1 but having an inneraperture 620 that is larger than inner aperture 120, as seen when viewedcross-sectionally along a direction of winding axis 104. Increasinginner aperture size increases cross-sectional area of magnetic fluxpaths, which increases inductance. Such increase in inductance decreasesthe resonant frequency and increases impedance at the resonantfrequency. Consequently, inductive-capacitive filter 600 will have alower resonant frequency and higher peak impedance thaninductive-capacitive filter 100.

As another example, FIG. 7 is a perspective view of aninductive-capacitive filter 700 which is like inductive-capacitivefilter 100 of FIG. 1 but having an inner aperture 720 that has an ovalshape instead of a circular shape, as seen when viewed cross-sectionallyalong a direction of winding axis 104. Although inner aperture 720 hasthe same circumference as inner aperture 120 of FIG. 1 , inner aperture720 has a smaller area than inner aperture 120, as seen when viewedcross-sectionally along a direction of winding axis 104. As a result,inductive-capacitive filter 700 will have a higher resonant frequencyand smaller peak impedance than inductive-capacitive filter 100. Any ofthe inductive-capacitive filters disclosed herein could be varied tohave a different inner aperture shape without departing from the scopehereof. For example, inductive-capacitive filter 700 could be modifiedsuch that inner aperture 720 has a different non-circular shape, such asa rectangular shape, a triangular shape, or even an irregular shape.

The material and/or thickness of insulating strip 108 could be modifiedin any of the inductive-capacitive filters disclosed herein, such as totune bandstop characteristics. Increasing the dielectric constant ofinsulating strip 108 decreases both the resonant frequency value and thepeak impedance of the inductive-capacitive filter. For example, FIG. 8is a perspective view of an inductive-capacitive filter 800 which islike inductive-capacitive filter 100 of FIG. 1 but with insulating strip108 replaced with an insulating strip 808. Insulating strip 808 has agreater dielectric constant than insulating strip 108. As a result,inductive-capacitive filter 800 will have a lower resonant frequency andsmaller peak impedance than inductive-capacitive filter 100. On theother hand, replacing insulating strip 108 with an insulating striphaving a lower dielectric constant than insulating strip 108 wouldincrease resonant frequency and peak impedance of inductive-capacitivefilter 100.

Increasing thickness 122 (FIG. 2 ) of insulating strip 108 increasesboth the resonant frequency value and the peak impedance of theinductive-capacitive filter. For example, FIG. 9 is a perspective viewof an inductive-capacitive filter 900 which is like inductive-capacitivefilter 100 of FIG. 1 but with insulating strip 108 replaced withinsulating strip 908. FIG. 10 is a cross-sectional view ofinductive-capacitive filter 900 taken along line 10A-10A of FIG. 9 .Insulating strip 908 has a thickness 922 that is greater than thickness122 of insulating strip 108. As a result, inductive-capacitive filter900 will have a lower capacitance, higher resonant frequency, andgreater maximum impedance than inductive-capacitive filter 100.

The material and/or thickness of conductive strip 110 could be modifiedin any of the inductive-capacitive filters disclosed herein, such as totune bandstop characteristics. For example, FIG. 11 is a perspectiveview of an inductive-capacitive filter 1100 which is likeinductive-capacitive filter 100 but with conductive strip 1110 replacingconductive strip 110. FIG. 12 is a cross-sectional view ofinductive-capacitive filter 1100 taken along line 12A-12A of FIG. 11 .Conductive strip 1110 has a thickness 1118 that is greater thanthickness 118 of conductive strip 110. Consequently,inductive-capacitive filter 1100 will have a smaller DC resistance andsmaller low frequency AC resistance than inductive-capacitive filter100.

Conductive strip 1110 has opposing first and second ends 1130 and 1132,respectively. A first terminal 1134 is electrically coupled to first end1130, and a second terminal 1136 is electrically coupled to second end1132. First and second terminals 1134 and 1136 provide electricalinterface to inductive-capacitive filter 1100. In some embodiments,first and second terminals 1134 and 1136 include a respective aluminumor copper buss bar or wire soldered to conductive strip 1110. First andsecond terminals 1134 and 1136 could be omitted without departing fromthe scope hereof.

The width of the insulating-conductive strip of any of theinductive-capacitive filters disclosed herein could also be modified totune bandstop characteristics. For example, increasing a width 124 (FIG.1 ) of insulating-conductive strip 102 increases surface area ofadjacent portions of conductive strip 110, thereby increasingcapacitance of inductive-capacitive filter 100 and reducing inductanceof the filter, resulting in a lower resonant frequency value and asmaller peak impedance. Additionally, increasing insulating-conductivestrip width 124 also reduces DC and low frequency AC resistance ofinductive-capacitive filter 100, which promotes ability ofinductive-capacitive filter 100 to transmit electrical energy withminimal loss. FIG. 13 is a perspective view of an inductive-capacitivefilter 1300 which is like inductive-capacitive filter 100 of FIG. 1 butwith an insulating-conductive strip 1302 replacing insulating-conductivestrip 102. Insulating-conductive strip 1302 is likeinsulating-conductive strip 102 but has a width 1324 that is greaterthan width 124 of insulating-conductive strip 102. Consequently,inductive-capacitive filter 1300 has a lower resonant frequency value,lower peak impedance, and lower resistance than inductive-capacitivefilter 100.

Any two or more of the inductive-capacitive filters disclosed hereincould be combined to form an inductive-capacitive filter assemblyincluding two inductive-capacitive filters in a single device, such asto achieve bandstop filtering across two or more frequency bands. Forexample, FIG. 14 is a perspective view of an inductive-capacitive filterassembly 1400 which includes a first insulating-conductive strip 1402and second insulating-conductive strip 1403 concentrically wound arounda winding axis 1404. First insulating-conductive strip 1402 is disposedwithin second insulating-conductive strip 1403, as seen wheninductive-capacitive filter assembly 1400 is viewed cross-sectionallyalong a direction of winding axis 1404. First insulating-conductivestrip 1402 forms a first inductive-capacitive filter 1405, and secondinsulating-conductive strip 1403 forms a second inductive-capacitivefilter 1407, such that inductive-capacitive assembly 1400 includes twoinductive-capacitive filters in a single device. Firstinsulating-conductive strip 1402 includes a first conductive stripjoined with a first insulating strip, where the first conductive stripis analogous to conductive strip 110 and the first insulating strip isanalogous to insulating strip 108. The first conductive strip and thefirst insulating strip are not labeled in FIG. 14 to promoteillustrative clarity. Similarly, second insulating-conductive strip 1403includes a second conductive strip (not labeled) and a second insulatingstrip (not labeled) which are also analogous to conductive strip 110 andinsulating strip 108, respectively.

Bandstop characteristics can be varied during the design and/ormanufacture of inductive-capacitive filter assembly 1400, for example,by (1) varying number of turns of first insulating-conductive strip 1402and/or second insulating-conductive strip 1403, (2) varying the sizeand/or shape of an inner aperture 1420 of inductive-capacitive filterassembly 1400, (3) varying thickness and/or dielectric properties of theinsulating strips, (4) varying the thickness of the conductive strips,and/or (5) varying a width 1424 of insulating-conductive strips 1402 and1403, such as in a manner similar to that discussed above with respectto FIGS. 1-13 . Additionally, although insulating-conductive strips 1402and 1403 are illustrated as forming three and four turns, respectively,the number of turns formed by insulating-conductive strips 1402 and 1403may be varied without departing from the scope hereof. Furthermore,inductive-capacitive filter assembly 1400 could be modified to includeone or more additional insulating-conductive strips, such that allinsulating-conductive strips are concentrically wound around windingaxis 1404, without departing from the scope hereof.

The inductive-capacitive filters of inductive-capacitive filter assembly1400 are optionally electrically coupled in series or parallel. Forexample, FIG. 15 illustrates inductive-capacitive filter assembly 1400with first insulating-conductive strip 1402 electrically coupled inseries with second insulating-conductive strip 1403 by an electricalconductor 1502. A first terminal 1534 is electrically coupled to a firstend of first insulating-conductive strip 1402, and a second terminal1536 is electrically coupled to a second end of secondinsulating-conductive strip 1403. First and second terminals 1534 and1356 provide electrical interface to inductive-capacitive filterassembly 1400. In some embodiments, first and second terminals 1534 and1536 include a respective aluminum or copper buss bar or wire. First andsecond terminals 1534 and 1536 could be omitted without departing fromthe scope hereof. FIG. 16 illustrates an approximate electrical model1600 of inductive-capacitive filter assembly 1400 electrically coupledas illustrated in FIG. 15 , as seen from first and second terminals 1534and 1536. Capacitor 1604 represents capacitance of firstinsulating-conductive strip 1402, inductor 1606 represents inductance offirst insulating-conductive strip 1402, and resistor 1608 representsresistance of first insulating-conductive strip 1402. Capacitor 1610represents capacitance of second insulating-conductive strip 1403,inductor 1612 represents inductance of second insulating-conductivestrip 1403, and resistor 1614 represents resistance of firstinsulating-conductive strip 1403.

FIG. 17 is a graph 1700 of impedance versus frequency of one particularembodiment of inductive-capacitive filter assembly 1400 with firstinsulating-conductive strip 1402 electrically coupled in series withsecond insulating-conductive strip 1403 as illustrated in FIG. 15 . Asevident from FIG. 17 , this particular embodiment has a first resonantfrequency 1702 of about 5.7 MHz and a second resonant frequency 1704 ofabout 15.6 MHz. First resonant frequency 1702 is a resonant frequencyassociated with second inductive-capacitive filter 1407, and secondresonant frequency 1704 is a resonant frequency associated with firstinductive-capacitive filter 1405. Peak impedance of firstinductive-capacitive filter 1405 is about 6,200 ohms at second resonantfrequency 1704, and peak impedance of second inductive-capacitive filter1407 is about 22,000 ohms at first resonant frequency 1702.

FIG. 18 illustrates inductive-capacitive filter assembly 1400 with firstinsulating-conductive strip 1402 electrically coupled in parallel withsecond insulating-conductive strip 1403 by an electrical conductors 1802and 1804, and FIG. 19 is a graph 1900 of impedance versus frequency ofone particular embodiment of inductive-capacitive filter assembly 1400with first insulating-conductive strip 1402 electrically coupled inparallel with second insulating-conductive strip 1403 as illustrated inFIG. 18 . As evident from FIG. 19 , this particular embodiment has aresonant frequency 1902 of 8.6 MHz and a peak impedance of about 6,600ohms at resonant frequency 1902.

FIG. 20 is a perspective view of a first inductive-capacitive filter2000 and a second inductive-capacitive filter 2001 electrically coupledin series by an electrical conductor 2026. Additional electricalconductors 2028 and 2030 provide electrical interface to first andsecond inductive-capacitive filters 2000 and 2001, respectively. Firstinductive-capacitive filter 2000 includes a first insulating-conductivestrip 2002, and second inductive-capacitive filter 2001 includes asecond insulating-conductive strip 2003. First insulating-conductivestrip 2002 includes an insulating strip 2008 wound in parallel with aconductive strip 2010 around a winding axis 2004, and secondinsulating-conductive strip 2003 includes an insulating strip 2009 woundin parallel with a conductive strip 2011 around a winding axis 2005.Each of the first insulating-conductive strip 2002 and secondinsulating-conductive strip 2003 has, for example, a configurationsimilar to one or more of the insulating-conductive strips discussedabove with respect to FIGS. 1-19 . Bandstop characteristics can bevaried during the design and/or manufacture of inductive-capacitivefilters 2000 and/or 2001, for example, by (1) varying number of turns offirst insulating-conductive strip 2002 and/or secondinsulating-conductive strip 2003, (2) varying the size and/or shape of ainner aperture 2020 and 2021 of inductive-capacitive filters 2000 and2001, (3) varying thickness and/or dielectric properties of insulatingstrip 2008 and/or insulating strip 2009, (4) varying thickness ofconductive strip 2010 and/or conductive strip 2011, and/or (5) and/orvarying a width 2024 and/or width 2025 of first and secondinsulating-conductive strip 2002 and 2003, respectively, such as in amanner similar to that discussed above with respect to FIGS. 1-19 .Additionally, although first and second insulating-conductive strips2002 and 2003 are illustrated as forming three and four turns 2006 and2007, respectively, the number of turns of first and secondinsulating-conductive strips 2002 and 2003 may be varied withoutdeparting from the scope hereof. Only some instances of turns 2006 and2007 are labeled in FIG. 20 to promote illustrative clarity.Furthermore, inductive-capacitive filter 2000 and/or 2001 could bemodified to include one or more additional insulating-conductive stripsdeparting from the scope hereof. Moreover, first inductive-capacitivefilter 2000 and a second inductive-capacitive filter 2001 could beelectrically coupled in parallel without departing from the scopehereof.

FIG. 21 is a graph 2100 of impedance versus frequency of one particularembodiment of the FIG. 20 inductive-capacitive filters 2000 and 2001electrically coupled in series. As evident from FIG. 21 , thisparticular embodiment has a first resonant frequency 2102 of about 2 MHzand a second resonant frequency 2104 of about 26.6 MHz. First resonantfrequency 2102 is a resonant frequency associated with secondinductive-capacitive filter 2001, and second resonant frequency 2104 isa resonant frequency associated with first inductive-capacitive filter2000. Peak impedance of first inductive-capacitive filter 2000 is about39,250 ohms at second resonant frequency 2104, and peak impedance ofsecond inductive-capacitive filter 2001 is about 16,095 ohms at firstresonant frequency 2102.

Any of the inductive-capacitive filters discussed above could bemodified to include one or more additional insulating-conductive strips.For example, FIG. 22 is a perspective view of an inductive-capacitivefilter assembly 2200 including three insulating-conductive strips 2202,and FIG. 23 is a cross-sectional view of inductive-capacitive filterassembly 2200 taken along line 23A-23A of FIG. 22 . Eachinsulating-conductive strip 2202 is similar to insulating-conductivestrip 102. In particular, first insulating-conductive strip 2202(1)includes a first conductive strip 2210(1) joined with a first insulatingstrip 2208(1), second insulating-conductive strip 2202(2) includes asecond conductive strip 2210(2) joined with a second insulating strip2208(2), and third insulating-conductive strip 2202(3) includes a thirdconductive strip 2210(3) joined with a third insulating strip 2208(3).In some embodiments, each conductive strip 2210 includes opposing firstand second terminals (not shown) electrically coupled to opposing endsof the conductive strip. Only some instances of insulating-conductivestrips 2202, insulating strips 2208 and conductive strips 2210 arelabeled in FIG. 23 to promote illustrative clarity. The number ofinsulating-conductive strips 2202 could be varied without departing fromthe scope hereof.

Each conductive strip 2210 is used, for example, as a separate channelof a multi-channel bandstop filter, where each channel has similarbandstop characteristics. Bandstop characteristics can be varied duringthe design and/or manufacture of inductive-capacitive filter assembly2200, for example, by (1) varying number of turns 2206 ofinsulating-conductive strips 2202, (2) varying the size and/or shape ofa inner aperture 2220 of inductive-capacitive filter assembly 2200, (3)varying thickness and/or dielectric properties of insulating strips2208, (4) varying thickness of conductive strips 2210, (5) and/orvarying a width 2224 of insulating-conductive strips 2202, such as in amanner similar to that discussed above with respect to FIGS. 1-21 . Onlytwo instances of turns 2206 are labeled in FIG. 22 to promoteillustrative clarity.

Inductive-capacitive filter assembly 2200 has an approximate electricmodel similar to that of FIG. 3 in applications where conductive strips2210 are electrically coupled in parallel. In contrast, FIG. 24illustrates an approximate electrical model 2400 of inductive-capacitivefilter assembly 2000 when conductive strips 2210 are not electricallycoupled in parallel. In this application, inductive-capacitive filterassembly 2200 forms three channels 2402, 2404, and 2406 corresponding toinsulating-conductive strips 2202(1), 2202(2), and 2202(3),respectively, such that each insulating-conductive strip 2202 forms arespective inductive-capacitive filter. Capacitor 2408, inductor 2410,and resistor 2412 represent capacitance, inductance, and resistance,respectively, of channel 2402. Capacitor 2414, inductor 2416, andresistor 2418 represent capacitance, inductance, and resistance,respectively, of channel 2404. Capacitor 2420, inductor 2422, andresistor 2424 represent capacitance, inductance, and resistance,respectively, of channel 2406. Capacitor 2426 represents capacitivecoupling between channel 2402 and channel 2404, capacitor 2428represents capacitive coupling between channel 2404 and channel 2406,and capacitor 2430 represents capacitive coupling between channel 2402and channel 2406. Although electrical model 2400 of FIG. 24 illustrateseach component being a discrete element for illustrative simplicity,each of these components represents a distributed element. Additionally,model 2400 does not account for high-order effects, such as a leakagecurrent through capacitors, capacitance of inductors, or inductance ofcapacitors.

Although the insulating strip and the conductive strip have a commonwidth in the illustrations of FIGS. 1, 2, 5-15, 18, 20, 22, and 23 ,insulating strip width and conductive strip width need not be the same.For example, FIG. 25 is a cross-sectional view analogous to FIG. 2 of aninductive-capacitive filter 2500 which is like the FIG. 1inductive-capacitive filter but including an insulating strip 2508 inplace of insulating strip 108. Insulating strip 2508 has a width 2516that is greater than a width 116 of conductive strip 110, such as toreduce the likelihood of accidental shorting of adjacent sections ofconductive strip 110.

Inductive-capacitive filters 100, 500, 600, 700, 800, 900, 1100, 1300,1405, 1407, 2000, 2001, 2200, and 2500 do not have an explicit magneticcore, or in other words, these inductive-capacitive filters have an“air” core. However, any of the inductive-capacitive filters disclosedherein could be modified to include an explicit magnetic core formed ofa magnetic material, including but not limited to a ferrite magneticmaterial or an iron powder magnetic material. The magnetic core, whichmay form either a partial magnetic flux path or a complete magnetic fluxpath, affects the resonant frequency of the inductive-capacitive filter.In particular, inductance increases with decreased reluctance of themagnetic flux path of the inductive-capacitive filter, and increasinginductance decreases the filter's resonant frequency. Consequently,resonant frequency of an inductive-capacitive filter with a givenmagnetic core can be tuned by varying magnetic permeability of magneticmaterial forming the magnetic core, such that resonant frequencydecreases with increasing magnetic permeability of the magneticmaterial.

FIG. 26 illustrates a perspective view of an inductive-capacitive filter2600 which is like inductive-capacitive filter 100 of FIG. 1 but furtherincluding a rod type magnetic core 2628 disposed in inner aperture 120.Rod type magnetic core 2628 forms only a partial magnetic flux path, orin other words, rod type magnetic core 2628 does not form a closed patharound resonant strip 102. Nevertheless, rod type magnetic core 2628significantly lowers reluctance of magnetic flux paths ofinductive-capacitive filter 2600 such that inductive-capacitive filter2600 has a lower resonant frequency than inductive-capacitive filter 100of FIG. 1 . First and second terminals 134 and 136 are not shown in FIG.26 to promote illustrative clarity.

FIGS. 27-29 each illustrate a respective example of aninductive-capacitive filter with a magnetic core forming a completemagnetic path, or in other words, with a magnetic core forming a closedpath around an insulating-conductive strip of the inductive-capacitivefilter. In particular, FIG. 27 illustrates a perspective view of aninductive-capacitive filter 2700 which is like inductive-capacitivefilter 100 of FIG. 1 but further including a magnetic core 2728.Magnetic core 2728 included an inner post (not visible in FIG. 27 )extending through inner aperture 120 and an outer portion connectingopposing ends of the inner post. In some embodiments, magnetic core 2728is formed of two “E” cores, and in some other embodiments, magnetic core2728 is formed of an “I” core and an “E” core. Magnetic core 2728provides a lower-reluctance magnetic flux path than magnetic core 2628of FIG. 26 , and therefore, inductive-capacitive filter 2700 of FIG. 27will have a lower resonant frequency than inductive-capacitive filter2600 of FIG. 26 . First and second terminals 134 and 136 are not shownin FIG. 27 to promote illustrative clarity.

FIG. 28 illustrates a perspective view of an inductive-capacitive filter2800 which is like inductive-capacitive filter 100 of FIG. 1 but furtherincluding a magnetic core 2828. In some embodiments, magnetic core 2828is formed of two “U” cores, and in some other embodiments, magnetic core2828 is formed of an “I” core and an “U” core. Magnetic core 2828provides a lower-reluctance magnetic flux path than magnetic core 2628of FIG. 26 , and therefore, inductive-capacitive filter 2800 of FIG. 28will have a lower resonant frequency than inductive-capacitive filter2600 of FIG. 26 . First and second terminals 134 and 136 are not shownin FIG. 28 to promote illustrative clarity.

FIG. 29 illustrates a perspective view of an inductive-capacitive filter2900 which is like inductive-capacitive filter 100 of FIG. 1 but furtherincluding a magnetic core 2928. Magnetic core 2928 is similar tomagnetic core 2728 of FIG. 27 but has a rounded outer portion connectingopposing ends of an inner post (not visible in FIG. 29 ) extendingthrough inner aperture 120. In some embodiments, magnetic core 2928 isformed of two pot cores. Magnetic core 2928 provides a lower-reluctancemagnetic flux path than either magnetic core 2628 of FIG. 26 , magneticcore 2728 of FIG. 27 , or magnetic core 2828 of FIG. 28 , and therefore,inductive-capacitive filter 2900 of FIG. 29 will have a lower resonantfrequency than either of inductive-capacitive filter 2600 of FIG. 26 ,inductive-capacitive filter 2700 of FIG. 27 , or inductive-capacitivefilter 2800 of FIG. 28 . First and second terminals 134 and 136 are notshown in FIG. 29 to promote illustrative clarity.

One possible application of the inductive-capacitive filters disclosedherein is in an electrical circuit, such as to implement a bandstopfilter which blocks signals having frequencies within a certainfrequency band around the filter's resonant frequency while transmittingsignals away from the resonant frequency. For example, FIG. 30illustrates an electrical circuit 3000 including an instance ofinductive-capacitive filter 100 electrically coupled in series with analternating current (AC) electrical power source 3002 and a load 3004.Circuit 3000 is, for example, part of a semiconductor processing system.In certain embodiments, electrical power source 3002 represents an ACelectric grid (e.g., operating at 50 or 60 Hertz), an AC generator, aninverter, an oscillator, an audio amplifier, or a radio-frequencyamplifier, and load 3004 represents a linear load (e.g., resistive,inductive, and/or capacitive load) or a non-linear load (e.g., aswitching power supply load). First end 130 of conductive strip 110 ofinductive-capacitive filter 100 is electrically coupled to electricalpower source 3002 via first terminal 134 at a first node 3006, andsecond end 132 of conductive strip 110 is electrically coupled to load3004 via terminal 136 at a second node 3008, in electrical circuit 3000.Thus first and second ends 130 and 132 of conductive strip 110 areelectrically coupled to different respective nodes 3006 and 3008 ofelectrical circuit 3000. In this particular application,inductive-capacitive filter 100 blocks transmission of signals within aparticular frequency band near filter 100's resonant frequency, such asto prevent transmission of undesired signals generated by electric powersource 3002 or by load 3004. Inductive-capacitive filter 100 is tuned,for example, to have a resonant frequency near or equal to the frequencyof the undesired signals, such that inductive-capacitive filter 100 hasa high-impedance at this frequency and thereby substantially blockstransmission of the undesired signals in electrical circuit 3000.

AC electrical power source 3002 could be replaced with a direct current(DC) electrical power source without departing from the scope hereof.For example, FIG. 31 illustrates an electrical circuit 3100 which islike electrical circuit 3000 of FIG. 30 but with AC electrical powersource 3002 replace with a direct current (DC) electric power source3102. DC electric power source 3102 is, for example, a DC electric powerbuss, a power supply, a battery, or one or more photovoltaic cells.

In a particular embodiment, load 3004 is a power supply which generatesan AC output signal at a frequency f₁ for powering external circuitry(not shown). This power supply is sensitive to noise from AC electricpower source 3002 or DC electric power source 2802 having a frequencyf₁, and inductive-capacitive filter 100 is accordingly tuned to blocktransmission of signals having a frequency f₁.

Electrical circuits 3000 and 3100 could be modified to replaceinductive-capacitive filter 100 with any of the otherinductive-capacitive filters disclosed herein without departing from thescope hereof. Additionally, the topology of electrical circuits 3000 and2100 could be modified without departing from the scope hereof. Forexample, electrical circuit 3000 could be modified such thatinductive-capacitive filter 100 is electrically coupled in parallel witheach of electrical power source 3002 and load 3104, to shunt all signalsexcept those having a frequency near the resonant frequency ofinductive-capacitive filter 100.

FIG. 32 illustrates an electrical circuit 3200 including an instance ofinductive-capacitive filter assembly 2200, an AC electrical power source3202, a first load 3204, a second load 3206, and a third load 3208.First channel 2402 of inductive-capacitive filter assembly 2200 iselectrically coupled between AC electrical power source 3202 and firstload 3204 in a first branch 3210 of electrical circuit 3200, secondchannel 2404 of inductive-capacitive filter assembly 2200 iselectrically coupled between AC electrical power source 3202 and secondload 3206 in a second branch 3212 of electrical circuit 3200, and thirdchannel 2406 of inductive-capacitive filter assembly 2200 iselectrically coupled between AC electrical power source 3202 and thirdload 3208 in a third branch 3208 of electrical circuit 3200. Circuit3200 is, for example, part of a semiconductor processing system. ACelectrical power source 3202 may be replaced with a DC electrical powersource without departing from the scope hereof.

In a particular embodiment, first load 3204 is a first power supplywhich generates an AC output signal at a first frequency f₁ for poweringexternal circuitry (not shown), second load 3206 is a second powersupply which generates an AC output signal at a second frequency f₂ forpowering external circuitry (not shown), and third load 3208 is a thirdpower supply which generates an AC output signal at a third frequency f₃for powering external circuitry (not shown). The first, second, andthird power supplies are sensitive to noise from AC electrical powersource 3202 having a frequency f₁, a frequency f₂, and a frequency f₃,respectively. Accordingly, first channel 2402 of inductive-capacitivefilter 2200 is tuned to block transmission of signals having a frequencyf₁, second channel 2404 of inductive-capacitive filter 2200 is tuned toblock transmission of signals having a frequency f₂, and third channel2406 of inductive-capacitive filter 2200 is tuned to block transmissionof signals having a frequency f₃, in this application.

FIG. 33 illustrates an electrical circuit 3300 including an instance ofinductive-capacitive filter assembly 1400, an AC electrical; powersource 3302, a load 3304. First and second inductive capacitive filters1405 and 1407 of assembly 1400 are electrically coupled in series withAC electrical power source 3302 and load 3304. Circuit 3300 is, forexample, part of a semiconductor processing system. AC electrical powersource 3302 may be replaced with a DC electrical power source withoutdeparting from the scope hereof.

In a particular embodiment, load 3304 is sensitive to noise from ACelectrical power source 3302 having a frequency f₁ and noise from ACelectrical power source 3302 having a frequency f₂. Accordingly, firstinductive-capacitive filter 1405 is tuned to block transmission ofsignals having a frequency f₁, and second inductive-capacitive filter1407 is tuned to block transmission of signals having a frequency f₂, inthis application.

Changes may be made in the above inductive-capacitive filters, systems,and associated methods departing from the scope hereof. It should thusbe noted that the matter contained in the above description and shown inthe accompanying drawings should be interpreted as illustrative and notin a limiting sense. The following claims are intended to cover genericand specific features described herein, as well as all statements of thescope of the present filters, methods, and system, which, as a matter oflanguage, might be said to fall there between

What is claimed is:
 1. An inductive-capacitive filter assembly,comprising: first and second insulating-conductive strips, each of thefirst and second insulating-conductive strips (a) having a firstinsulating strip joined with a first conductive strip and a secondinsulative strip joined with a second conductive strip and (b) wound inseries about a common winding axis, such that the inductive-capacitivefilter assembly blocks signals with frequencies centered around firstand second resonant frequencies when (i) a first terminal end of thefirst conductive strip connects to a power source, (ii) a secondterminal end of the first conductive strip connects to a first terminalend of the second conductive strip by a conductor, and (iii) a secondterminal end of the second conductive strip connects to a load.
 2. Theinductive-capacitive filter assembly of claim 1, the first and secondinsulating-conductive strips layered together and wound about thewinding axis, each of the first and second insulating-conductive stripsbeing tuned to one of the frequencies according to one or more of:number of turns of insulating conductive strips, size and shape of aninner aperture of the inductive-capacitive filter assembly, insulatingstrip dielectric properties and thickness, conductive strip thickness,width of the insulating-conductive strips, and a combination thereof. 3.The inductive-capacitive filter assembly of claim 1, wherein eachconductive strip comprises metallic foil and each insulating stripcomprises dielectric material.
 4. The inductive-capacitive filterassembly of claim 1, wherein each conductive strip has a cross-sectionalarea with an aspect ratio of at least
 2. 5. The inductive-capacitivefilter assembly of claim 1, wherein the first and secondinsulating-conductive strips form an inner aperture, as seen when theinductive-capacitive filter assembly is viewed cross-sectionally along adirection of the winding axis.
 6. The inductive-capacitive filterassembly of claim 5, wherein the inner aperture has size andnon-circular shape contributing in part to tuning theinductive-capacitive filter to the resonant frequencies.
 7. Theinductive-capacitive filter assembly of claim 5, further comprising amagnetic core disposed in the inner aperture that in part tunes theinductive-capacitive filter to its resonant frequencies.
 8. Theinductive-capacitive filter assembly of claim 1, the first and secondinsulating-conductive strips having a different respective number ofturns around the winding axis, wherein the number of turns contribute totuning of the resonant frequencies.
 9. An inductive-capacitive filterassembly, comprising: first and second insulating-conductive strips,each of the first and second insulating-conductive strips (a) having afirst insulating strip joined with a first conductive strip and a secondinsulative strip joined with a second conductive strip and (b) wound inparallel about a common winding axis, such that the inductive-capacitivefilter assembly blocks signals with frequencies centered around firstand second resonant frequencies when (i) a first conductor connects afirst terminal end of the first conductive strip with a first terminalend of the second conductive strip, (ii) a second conductor connects asecond terminal end of the first conductive strip to a second terminalend of the second conductive strip, (iii) the first terminal ends of thefirst and second conductive strip connects to a power source, and (iv)the second terminal ends of the first and second conductive stripsconnect to a load.
 10. The inductive-capacitive filter assembly of claim9, the first and second insulating-conductive strips layered togetherand wound about the winding axis, each of the first and secondinsulating-conductive strips being tuned to one of the frequenciesaccording to one or more of: number of turns of insulating conductivestrips, size and shape of an inner aperture of the inductive-capacitivefilter assembly, insulating strip dielectric properties and thickness,conductive strip thickness, width of the insulating-conductive strips,and a combination thereof.
 11. The inductive-capacitive filter assemblyof claim 9, wherein: each conductive strip comprises metallic foil; andeach insulating strip comprises dielectric material.
 12. Theinductive-capacitive filter assembly of claim 9, wherein each conductivestrip has a cross-sectional area with an aspect ratio of at least
 2. 13.The inductive-capacitive filter assembly of claim 9, wherein the firstand second insulating-conductive strips form an inner aperture, as seenwhen the inductive-capacitive filter assembly is viewedcross-sectionally along a direction of the winding axis.
 14. Theinductive-capacitive filter assembly of claim 13, wherein the inneraperture has size and non-circular shape contributing in part to tuningthe inductive-capacitive filter to the resonant frequencies.
 15. Theinductive-capacitive filter assembly of claim 13, further comprising amagnetic core disposed in the inner aperture that in part tunes theinductive-capacitive filter to its resonant frequencies.
 16. Theinductive-capacitive filter assembly of claim 9, the first and secondinsulating-conductive strips each forming a different respective numberof turns around the winding axis wherein the number of turns contributeto tuning to each of the resonant frequencies.